Angle-Dependent Light Scattering Study of Silica Aggregate Growth in 1-D Methane/Air Flames with Hexamethyldisiloxane Admixture: Effects of Siloxane Concentration, Flame Temperature, and Equivalence Ratio

Silica aggregate formation was studied in 1D premixed methane/hexamethyldisiloxane/air flames by angle-dependent light scattering measurements for various siloxane concentrations, flame temperatures, and equivalence ratios, using Guinier analysis to interpret the experimental data. A sublinear dependence of the aggregate radii of gyration R-g of generated silica particles on residence time, and non-monotonic dependence on flame temperature with a maximum around 2000 K have been observed, with radii of gyration Rg in the range of 10 to 120 nm. Furthermore, a lean flame environment appears to foster aggregate growth compared to rich and stoichiometric flames, in which growth is very similar. When fixing the initial conditions at the residence time corresponding to the first measurement point, a simple model describing particle evolution as a result of collisional growth and sintering predicts well the functional dependence of the growth of particle radii.